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Title: Poster — Thur Eve — 72: Clinical Subtleties of Flattening-Filter-Free Beams

Flattening-filter-free (fff) beams offer superior dose rates, reducing treatment times for important techniques that utilize small field sizes, such as stereotactic ablative radiotherapy (SABR). The impact of ion collection efficiency (P{sub ion}) on the percent depth dose (PDD) has been discussed at length in the literature. Relative corrections of the order of l%–2% are possible. In the process of commissioning 6fff and 10fff beams, we identified a number of other important details that influence commissioning. We looked at the absolute dose difference between corrected and uncorrected PDD. We discovered a curve with a broad maximum between 10 and 20 cm. We wondered about the consequences of this PDD correction on the absolute dose calibration of the linac because the TG-51 protocol does not correct the PDD curve. The quality factor k{sub Q} depends on the PDD, so in principle, a correction to the PDD will alter the absolute calibration of the linac. Finally, there are other clinical tables, such as TMR, which are derived from PDD. Attention to details on how this computation is performed is important because different corrections are possible depending the method of calculation.
Authors:
; ;  [1]
  1. BC Cancer Agency, Fraser Valley Centre, 13750 9"t"h Ave Surrey, BC (United Kingdom)
Publication Date:
OSTI Identifier:
22407694
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 41; Journal Issue: 8; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
07 ISOTOPES AND RADIATION SOURCES; CALIBRATION; COMMISSIONING; DEPTH DOSE DISTRIBUTIONS; DOSE RATES; LINEAR ACCELERATORS; RADIOTHERAPY